The present invention relates to a process for preparing polyamides from dinitriles and diamines and water at elevated temperature and elevated pressure.
It is an object of the present invention to provide a process for preparing polyamides from dinitriles and diamines and water in a good space-time yield with straightforward catalyst removal.
We have found that this object is achieved by a process for preparing a polyamide by reacting at least one dinitrile and at least one diamine with water at a temperature from 90 to 400xc2x0 C. and a pressure from 0.1 to 50*106 Pa in a molar ratio of at least 1:1 for water to the sum total of dinitrile and diamine in the presence of a heterogeneous catalyst selected from the group consisting of aluminum oxide, tin oxide, silicon oxide, oxides of the second to sixth transition group of the periodic table, oxides of the lanthanides and actinides, sheet-silicates and zeolites.
The invention further provides a continuous process for preparing a polyamide by reacting at least one dinitrile and at least one diamine with water, which comprises:
(1) reacting at least one dinitrile and at least one diamine with water at a temperature from 90 to 400xc2x0 C. and a pressure from 0.1 to 35xc3x97106 Pa in a flow tube containing a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide to obtain a reaction mixture,
(2) further reacting the reaction mixture at a temperature from 150 to 400xc2x0 C. and a pressure which is lower than the pressure in stage 1 in the presence or absence of a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, the temperature and pressure being selected so as to obtain a first gas phase and a first liquid or a first solid phase or a mixture of first solid and first liquid phases, and the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phases, and
(3) admixing the first liquid or the first solid phase or the mixture of first liquid and first solid phases with a gaseous or liquid phase comprising water at a temperature from 150 to 370xc2x0 C. and a pressure from 0.1 to 30xc3x97106 Pa to obtain a product mixture.
The invention further provides a continuous process for preparing a polyamide by reacting at least one dinitrile and at least one diamine with water, which comprises:
(1) reacting at least one dinitrile and at least one diamine with water at a temperature from 90 to 400xc2x0 C. and a pressure from 0.1 to 35xc3x97106 Pa in a flow tube containing a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide to obtain a reaction mixture,
(2) further reacting the reaction mixture at a temperature from 150 to 400xc2x0 C. and a pressure which is lower than the pressure in stage 1 in the presence or absence of a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, the temperature and pressure being selected so as to obtain a first gas phase and a first liquid or a first solid phase or a mixture of first solid and first liquid phases, and so that the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phases, and
(3) admixing the first liquid or the first solid phase or the mixture of first liquid and first solid phases with a gaseous or liquid phase comprising water at a temperature from 150 to 370xc2x0 C. and a pressure from 0.1 to 30xc3x97106 Pa in a flow tube containing a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or a titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide maybe replaced by tungsten oxide to obtain a product mixture.
The above processes preferably further comprise the following stage:
(4) postcondensing the product mixture at a temperature from 200 to 350xc2x0 C. and a pressure which is lower than the pressure in stage 3, the temperature and pressure being selected so as to obtain a second, water- and ammonia-containing gas phase and a second liquid or second solid phase or a mixture of second liquid and second solid phases, which each include the polyamide.
The invention further provides a continuous process for preparing a polyamide by reacting at least one dinitrile and at least one diamine with water, which comprises:
(1) reacting at least one dinitrile and at least one diamine with water at a temperature from 90 to 400xc2x0 C. and a pressure from 0.1 to 35xc3x97106 Pa in a flow tube containing a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicates catalyst or a titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide to obtain a reaction mixture,
(2) further reacting the reaction mixture at a temperature from 150 to 400xc2x0 C. and a pressure which is lower than the pressure in stage 1 in the presence or absence of a Brxc3x6nsted acid catalyst selected from a beta-zeolite catalyst, a sheet-silicate catalyst or titanium dioxide catalyst comprising from 70 to 100% by weight of anatase and from 0 to 30% by weight of rutile and in which up to 40% by weight of the titanium dioxide may be replaced by tungsten oxide, the temperature and pressure being selected so as to obtain a first gas phase and a first liquid or first solid phase or a mixture of first solid and first liquid phases, and so that the first gas phase is separated from the first liquid or the first solid phase or from the mixture of first liquid and first solid phases, and
(4) postcondensing the first liquid or the first solid phase or the mixture of first liquid and first solid phases at a temperature from 200 to 350xc2x0 C. and a pressure which is lower than the pressure in stage 3, the temperature and pressure being selected so as to obtain a second, water- and ammonia-containing gas phase and a second liquid or second solid phase or a mixture of second liquid and second solid phases, which each include the polyamide.
The principle of the process of the invention is described in prior DE-A-19 804 023, unpublished at the priority date of the present invention.
The dinitrile used may in principle be any dinitrile, i.e., any compound containing at least two nitrile groups, singly or mixed, alpha,omega-Dinitriles are preferred, especially alpha,omega-alkylenedinitriles having from 3 to 12 carbon atoms, more preferably from 3 to 9 carbon atoms, in the alkylene moiety, or alkylaryl dinitriles having from 7 to 12 carbon atoms, preferred alkylaryl dinitriles being alkylaryl dinitriles which have an alkylene group of at least one carbon atom between the aromatic unit and the two nitrile groups. Especially preferred, alkylaryl dinitriles are those which have the two nitrile groups in the 1,4 position relative to each other.
Useful alpha,omega-alkylenedinitriles preferably further include linear alpha,omega-alkylenedinitriles in which the alkylene moiety (xe2x80x94CH2xe2x80x94) preferably contains from 3 to 11 carbon atoms, more preferably from 3 to 9 carbon atoms, such as 1,3-dicyanoprope, 1,4-dicyanobutane (adiponitrile, ADN), 1,5-dicyanopentane, 1,6-dicyanohexane, 1,7-dicyanoheptane, 1,8-dicyanooctane, 1,9-dicyannonane, particularly preferably adiponitrile,
adiponitrile may be obtained in a conventional manner by double catalytic addition of HCN to butadiene.